HIRANUMA APPLICATION DATA

Factorstandardization

Automatic Titrator

Data No.

O6Feb. 03,
2022

Standardization of sodium acetate titrant

1. Abstract
Non-aqueous titration using a 0.1 mol/L perchloric acid-acetic acid solution (hereinafter referred to asperchloric acid titration) has been used for test methods such as JIS K2501 “Petroleum products and lubricants– Determination of neutralization number” and determination of purity for some substance in the JapanesePharmacopoeia. Weakly basic components that hardly react with a titrant in water can be quantified byneutralization titration with the perchloric acid titration. When a clear inflection point is not obtained withnormal perchloric acid titration, back titration method combined with perchloric acid titration is used.
In the back titration method of perchloric acid titration, 0.1 mol/L sodium acetate-acetic acid solution isused as the titrant. An excessive amount of 0.1 mol/L perchloric acid-acetic acid solution is added to the sample
to react with target component, and the remaining perchloric acid is titrated with sodium acetate-acetic acidsolution to indirectly quantify the target component. Therefore, it is necessary to standardize the sodium
acetate-acetic acid solution before performing the back titration.
A standardized perchloric acid-acetic acid solution is used for the factor determination of the sodium
acetate-acetic acid solution. Please refer to the application Data No. B20 for the method of standardizing
perchloric acid-acetic acid solution.
The method for preparing and standardizing the sodium acetate-acetic acid solution is different between
the Japanese Pharmacopoeia and JIS K2501. In the Japanese Pharmacopoeia, sodium acetate-acetic acidsolution is added to the titration vessel as a sample and titrated with perchloric acid-acetic acid solution. On theother hand, in JIS K2501, perchloric acid-acetic acid solution is used as a sample and titrated with sodium
acetate-acetic acid solution. Moreover, JIS K2501 describes two procedures, A and B, in which the amount of
titration solvent is different in the standardization. In this report, the factors of the sodium acetate-acetic acidsolution were standardized by two different method in reference to the Japanese Pharmacopoeia and JIS
K2501 (Procedure A), respectively. 1 mol of perchloric acid and 1 mol of sodium acetate react quantitatively
according to formula (1), and the titration curve shows an inflection point at the end point.
HClO4 ＋ CH3COONa → NaClO4 ＋ CH3COOH
1) Japanese Pharmacopoeia Eighteenth Edition
2) Japanese Industrial Standard JIS K2501

2. Configuration of instruments and reagents(1) Configuration of instruments
Main unit: Automatic Titrator

COM Series

Optional buret

1 unit･･･(1)Electrodes: Glass electrodeGE-101B

Reference electrodeRE-201Z

Inner solution of RE-201Z is replaced to a saturated sodium perchlorate-acetic
acid solution.
* It can also be applied to glass-reference combination electrode GR-511BZ.
(2) Reagents
Titrant: 0.1 mol/L (0.1 N) sodium acetate-acetic acid solution (Buret No. 2)
Preparation procedure on Japanese Pharmacopoeia
Dissolve 8.2 g of sodium acetate anhydrous in acetic acid,and dilute to 1 L with acetic acid.
Preparation procedure on JIS K2501
Dissolve 5.3 g of sodium carbonate anhydrous in acetic acid,and dilute to 1 L with acetic acid.

Standard sample: 0.1 mol/L (0.1 N) perchloric acid-acetic acid solution (f = 1.000, Buret No.1)

Titration solvent: Acetic acid (Japanese Pharmacopoeia)
Mixture of 500 mL of glacial acetic acid and 1 L of toluene (JIS K2501)

3. Measurement procedure(1) Standardization procedure according to Japanese Pharmacopoeia.
i) Add 50 mL of acetic acid and a stirrer bar to a 100 mL beaker.
ii) Immerse the electrodes and start the measurement.
iii) 10 mL(*a) of 0.1 mol/L sodium acetate-acetic acid solution is added to the beaker by the buret
dispensing.
iv) Titration is subsequently performed with 0.1 mol/L perchloric acid-acetic acid solution. The inflection
point on the titration curve is detected as the end point.
v) Perform a blank test by the same operation except iii).
*a: It is described as 25 mL in Japanese Pharmacopoeia. In this report, it was set to 10 mL to savereagents.
(2) Standardization procedure according to JIS K2501 with procedure A.
i) Add 120 mL(*b) of titration solvent and a stirrer bar to a 200 mL tall beaker.
ii) Immerse the electrodes and start the measurement.
iii) 10 mL(*c) of 0.1 mol/L perchloric acid-acetic acid solution is added to the beaker by the buret
dispensing.
iv) Titration is subsequently performed with 0.1 mol/L sodium acetate-acetic acid solution. The inflection
point on the titration curve is detected as the end point.
v) Perform a blank test by the same operation except iii).
*b: It is described as 120 mL in the procedure A and 60 mL in the procedure B of JIS K2501.
*c: It is described as 8 mL in the procedure A and 4 mL in the procedure B of JIS K2501. In thisreport, it was set to 10 mL in order to make it same to as (1).

4. Measurement conditions and results
Examples of titration conditions(1) Blank of Japanese Pharmacopoeia
1M. File1Cndt No.
116 *1
MethodAutoConstantNo.
Mode No.
10 mL
0 sec
Buret No.
Size
Pre Int
10 mL
0Amp No.
Blank
Del KmV
0.1 mol/L Del Sens
0 mV
D. Unit
Molarity
5 Sec
03 sec
S-Timer
Factor
Int Time
0.0 mL
05 mV
C.P. mLK
Int Sens
0sec
02T Timer
LBrt Speed
0.0 mL
16D.P. mL
Pulse
200mL
End Sens
Unit
0.50 mL
D
Over mL
Formula
1mL
4Max.Vol.
Digits
*1: Since the maximum change in electrode potential is shown at the first drop of this blank titration, theend point is detected in the first drop or less volume. To detect this maximum change as an end point, set
Mode No. to which the blank mode function is assigned, Mode No.12-19 for COM-A19.
(2) Factor standardization of Japanese Pharmacopoeia

M. File2+3
Cndt No.
2
MethodDispBuret No.
2S-Timer
5 sec
Disp Vol.
10 mL
Cndt No.
3
MethodAutoConstantNo.
3
Buret No.
1Size
10 mL
Amp No.
1Blank
0.01 mL
D. UnitmVMolarity
0.1 mol/L
S-Timer
5 sec
Factor1.000 *2
C.P. mL0 mLK0T Timer0 sec
L
0D.P. mL
1.0 mLEnd Sens
200UnitFact
Over mL
0.5 mL
Formula(D-B)/S*F
Max.Vol.
20 mLDigits
4*2: Factor of 0.1 mol/L perchloric acid-acetic acid solution

Mode No.
Pre Int
Del K
Del Sens
Int Time
Int Sens
Brt SpeedPulse

2105035240sec
mVsec
mV

(3) Blank of JIS K2501
4M. File
4Cndt No.
416 *3
MethodAutoConstantNo.
Mode No.
20 mL
0 sec
Buret No.
Size
Pre Int
10 mL
0Amp No.
Blank
Del KmV
0.1 mol/L Del Sens0 mV
D. Unit
Molarity
5Sec03 sec
S-TimerFactor
Int Time0.0mL
05 mV
C.P. mL
KInt Sens
0 sec
02T Timer
LBrt Speed
0.0 mL
16D.P. mL
Pulse
200mL
End Sens
Unit
0.50mLD
Over mL
Formula
1 mL
4Max.Vol.
Digits*3: Since the maximum change in electrode potential is shown at the first drop of this blank titration, theend point is detected in the first drop or less volume. To detect this maximum change as an end point, set
Mode No. to which the blank mode function is assigned, Mode No.12-19 for COM-A19.
(4) Factor standardization of JIS K2501

M. File5+6Cndt No.
5Method
DispBuret No.
1S-Timer
5 sec
Disp Vol.
10 mL
Cndt No.
6Method
AutoConstantNo.
6Buret No.
2Size
10 mL
Amp No.
1Blank
0.01 mL
D. UnitmVMolarity
0.1 mol/L
S-Timer
5 sec
Factor1.000 *4
C.P. mL
0 mL
K0T Timer
0 sec
L0D.P. mL
1.0 mLEnd Sens
200Unit
Fact1
Over mL
0.5 mL
FormulaS/(D-B)*F
Max.Vol.
20 mL
Digits
4*4: Factor of 0.1 mol/L perchloric acid-acetic acid solution

Mode No.
Pre IntDel KDel Sens
Int TimeInt Sens
Brt SpeedPulse

2105035240secmVsecmVMeasurement results
Measurement result of factor standardization for sodium acetate-acetic acid solution
Titrant
Measurement Sample
ProcedureSample
volumeFactor Statistic calculation
No.
size (mL)
(mL)
Blank
10.010Japanese
Factor1109.628
0.9618 Avg.
0.962
Pharmacopoeia
2109.630
0.9620 SD
0.00013109.629
0.9619 RSD
0.01 %Blank
10.010JIS K2501
Factor11010.0340.9976 Avg.
0.997
210
10.0390.9971 SD
0.0004310
10.0420.9968 RSD
0.04 %

Japanese Pharmacopoeia (Left)Blank、(Right)Factor

JIS K2501(Left)Blank、(Right)Factor

Examples of titration curves

5. Note(1) About the factor calculation formula of the sodium acetate-acetic acid solution of the JapanesePharmacopoeia
In measurement of the factor standardization, there are many case examples of titrating a standard materialusing the titrant to be standardized. In the Japanese Pharmacopoeia procedure for sodium acetate-acetic acidsolution, the titrant and the sample are reversed. The perchloric acid-acetic acid solution is used as the titrant,
and the sodium acetate-acetic acid solution to be standardized is used as the sample for titration.
In this case, the factor calculation formula is set as [(D-B)/S*F]. This formula is not initially installed in thetitrator and must be set using the formula editing function.
The calculation formula is derived based on the following relational formula (2). The left side (subscript s) isthe titrant of perchloric acid-acetic acid solution and has already been standardized preliminary, and the rightside (subscript t) is the sample of sodium acetate-acetic acid solution to be standardized.
ns × Ms ×Fs × (D - B) = nt × Mt × Ft × S
Perchloric acid・・・(2)Sodium acetate

ns：Valence (1)nt：Valence (1)Ms：Molar concentration (0.1)

Mt：Molar concentration (0.1)

Fs：Factor (Known)

Ft：Factor (Unknown)

D-B：Titrant volume (mL)

S：Sample size (mL)(2) Tips for perchloric acid titration
Perchloric acid titration is a non-aqueous titration, so if water gets into the sample solution, the inflection pointon titration curve at the end point become unclear. Therefore, it is necessary to replace the inner solution of thereference electrode from potassium chloride aqueous solution to the saturated sodium perchlorate-acetic acidsolution.
Since the perchloric acid-acetic acid solution and sodium acetate-acetic acid solution consist of organic
solvents, the volume expansion due to temperature change is 0.11% per 1 °C, which is larger than that of theaqueous solution. Therefore, it is important to keep the same temperature as much as possible through thestandardization of perchloric acid standard solution, the standardization of sodium acetate standard solution,and the measurement of the sample. Please refer to Application Data No. B19 and 20, which explain this indetail.
Keywords：Factor standardization, Non-aqueous titration, Perchloric acid titration, Back-titration, Sodium acetate,
JIS K2501, Japanese Pharmacopoeia*Some measurement would not be possible depending on optional configuration of system.